Cheddar, Leek & Mushroom Pie

1. Warm your oven to 200°C/Fan 180°C/Gas 6. Trim the roots and woody greens off the leeks, then rinse out any grit. Thinly slice the leeks. Slice or tear the chestnut mushrooms into small pieces. Pick the thyme leaves off their woody stems. Peel and thinly slice the garlic cloves. Coarsely grate the cheddar into a bowl and set to one side.

2. Pour 1 tbsp oil into a large pan and warm over a medium heat. Slide in the chopped leeks, mushrooms, thyme and garlic. Season with salt and pepper, pop on a lid and cook for 6-8 mins, stirring occasionally, till juicy.

3. While the veg cook, scrub the potatoes (no need to peel, but you can if you prefer) and slice them as thinly as possible. If you have a mandoline or slicing attachment on your food processor, you can use that to speed up the process.

4. Slide the sliced potatoes into a large, clean pan and pour in enough cold water to just cover them. Add a pinch of salt and bring to the boil. Once boiling, turn the heat down and simmer the potatoes for 2-3 mins, till just tender but still holding their shape. Drain and rinse with cold water. Gently shake dry and pop to one side.

5. When the mushrooms and leeks are tender, add the cornflour to the pan and stir well for 1 min to coat the veg. Slowly pour in the milk, a little at a time and stirring as you pour, till the cornflour and milk combine to make a smooth sauce.

6. Warm the sauce to a simmer, then stir in the grated cheddar and baby laf spinach. Cook and stir for 1-2 mins till the spinach has wilted.

7. Scoop the vegetables and cheese sauce into a medium-sized ovenproof pie or casserole dish and level it with the back of a spoon. Layer the thinly sliced potatoes over the top, till evenly covered. Drizzle 1 tbsp oil over the top of the potatoes and season with salt and pepper. Slide the dish into the oven and bake for 25-30 mins, till golden and bubbling. When the pie is ready, let it sit for a couple of minutes, then serve with seasonal veg.

8. Get Ahead
You can assemble the pie the night before you want to serve it. Cook the filling and top with the potato slices, then cool and store the dish in the fridge, ready to bake in the oven for 30-40 mins (if cooking from chilled) till browned and piping hot al the way through.

9. Love Your Leftovers
The pie will keep for up to 3 days in the fridge either in the dish, covered with food wrap, or in airtight tubs. Reheat in the microwave or in the oven, loosely covered with foil to protect the top from burning, till piping hot. The pie can also be frozen for up to 3 months. Defrost overnight before reheating.